package com.chenglu.android.restaurant.shop.view;

import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;

import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.LinearSmoothScroller;
import androidx.recyclerview.widget.RecyclerView;

public class CenterLayoutManager  extends LinearLayoutManager {
    public CenterLayoutManager(Context context) {
        super(context);
    }

    public CenterLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    public CenterLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        CenterSmoothScroller smoothScroller = new CenterSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

     class CenterSmoothScroller extends LinearSmoothScroller{


         public CenterSmoothScroller(Context context) {
             super(context);
         }

         @Override
         public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) {
             return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
         }

         @Override
         protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
             return 100f / displayMetrics.densityDpi;
         }
     }


}
